1. Field of the Invention
The present general inventive concept relates to an image forming apparatus and a control method thereof to control rotation of an agitator used to feed developer into a developing region of the image forming apparatus.
2. Description of the Related Art
Generally, image forming apparatuses are devised to develop a black-and-white image or color image on a printing medium, such as paper, according to image signals. Examples of image forming apparatuses include Light Emitting Diode (LED) printers, laser printers, inkjet printers, copiers, facsimiles, and so-called multi-functional devices that combine some of the functionalities of the aforementioned devices.
In an electro-photographic image forming apparatus as a kind of the aforementioned image forming apparatuses, after a surface of a photoconductor is charged by an electric potential or is subjected to a cleaning operation, developer is attached to a region resulting from an electric potential difference on the surface of the photoconductor to form a visible image. The visible developer image, formed on the photoconductor, is transferred to a printing medium, and thereafter is fused to a surface of the printing medium upon receiving heat and pressure.
Developer used for image development may be classified into single component developers and binary developers. In the case of single component developers, after toner particles are charged by friction therebetween or friction with another charging member, the charged toner particles are delivered to a developing roller, and then are attached to the photoconductor. Binary developer is prepared by mixing a magnetic carrier and a non-magnetic synthetic resin toner at an appropriate mixing ratio. Toner particles are charged upon mixing with carrier particles and are delivered to a magnetic roller together with the carrier particles to thereby be attached to the photoconductor.
A developing unit using binary developer receives toner from a toner feed vessel replaceably mounted in a body of the image forming apparatus. Toner particles fed from the toner feed vessel are mixed with carrier particles by an agitator provided in a housing of the developing unit and are charged with a polarity opposite to the carrier particles. The agitator includes a pair of augers. A first one of the pair of augers delivers newly fed toner particles in a given direction to mix the toner particles with the carrier particles and electrically charge the toner particles. A second auger is spaced apart from the magnetic roller with a predetermined gap and delivers the mixed developer in an opposite direction to uniformly feed the developer throughout a surface of the magnetic roller.
The housing of the developing unit is divided into a first agitation space in which the first auger is rotatably provided, and a second agitation space in which the second auger is rotatably provided. The two agitation spaces are connected to each other through two gates defined in opposite sides of the housing. Thus, the developer is fed to the magnetic roller while circulating in the two agitation spaces.
However, if the developing unit is tilted during transportation or storage thereof, or if vibration or irregular operation of the two augers occurs, the developer may be concentrated on one of the gates. This may prevent the developer from being smoothly delivered through the gates when the developer unit is initially operated after installation thereof. As a result, the gates may undergo increased developer delivery pressure and the rotating augers may exhibit significantly increased torque. Such a pressure or torque increase may damage, e.g., a drive motor provided in a body of the image forming apparatus as well as constituent elements of the developing unit, such as the augers, housing, and other components of the developing unit.